In some clinical situations it is necessary to intervene to ensure that the urethra remains open. Such is the case, for example, in various pathologies associated with swelling of the prostate in males. One means for achieving this is by deploying a stent at the appropriate place inside the urethra.
Stents are typically made of a helical wire or band which once deployed inside a tubular organ expands to the desired diameter thereby supporting the walls of the organ. U.S. Pat. No. 5,037,427 discloses a stent made of a two-way shape memory alloy and means for its deployment in and recovery from a tubular organ. The stent in accordance with this patent has a transition temperature which is below the body temperature in which it changes in diameter from a narrow diameter to a wide diameter in which it attaches to the wails of the tubular organ. The stent is inserted into the tubular organ under a constant flow of cold fluid and once the correct position of the stent is reached, the flow of the cold fluid is stopped and the stent then expands under the influence of the body temperature. For removal, the stent is cooled again and withdrawn under a continuous application of cold fluid. It will no doubt be appreciated that a continuous application of a cold fluid may not always be practicable and this is a continuous drawback for various applications.
PCT Application, WO 93/13824, discloses a segmentally expandable stent comprising a helically coiled structure shaped wire of an nickel-titanium alloy (Nitinol.TM.). In its primary shape its diameter in at least a portion is wide so as to support the walls of the urethra and in its other state the diameter is reduced to an extent allowing insertion of the stent into the urethra. The stent is designed in a manner that it does not change in length upon expansion. However, the big disadvantage of such a stent is in that the wires press on the surrounding tissue at relatively large local pressure which can damage this delicate tissue. Furthermore, after some times of being within the urethra, there is a growth of tissue in the gaps between the wires, which hinders easy removal of the stent.
Placing a stent in the appropriate place in the urethra poses a special problem to the practitioner of proper localization. For example, in male subjects suffering from a prostate enlargement, it is necessary to place the stent at the right zone of the urethra within the prostate as improper placement will not yield the desired result of ensuing urine drainage.
It is an object of the present invention to provide a novel urological stent. It is particularly an object of the invention to provide such a stent which can be easily deployed in the urethra and easily removed therefore.
It is another object of the invention to provide a device adapted for deployment of the stent within the urethra in a manner which will ensure proper positioning of the stent.